Royal Icing: Humidity and Royal Icing Storage

Humidity, whether present when you decorate with Royal Icing, when you serve your decorated cookies, or when you store your icing transfers or cookies themselves, will ruin your work.

This article is about how to prevent problems related to humidity, and possibly how to fix damaged icing or cookies due to humidity. The good thing about decorating with Royal Icing, however, if all goes wrong, you can always eat your work.

For starters, here is a list of never do-es:

  • If your environment is not air conditioned, avoid decorating cookies when the humidity is over 70%: High humidity softens sugar cookies and prohibits icing from quickly drying, which leads to mottled colors that run into each other.
  • Even if it is cool out and you must make cookies in high-humidity weather, consider running your air conditioner. Wear a sweater if needed.
  • Never put a plate of beautifully decorated cookies out in a hot, high-humidity atmosphere (like at a lake-side picnic) as they will turn soft.
  • If you transport cookies, do not do it in a hot environment.
  • If you transport cookies by mail, make sure every cookie is completely dry and packaged in some type of air-tight container. Consider placing a silicon “anti-humidity” packets in the container, too.
  • Do not refrigerate or freeze Royal Icing or cookies unless everything is sealed in air-tight containers along with silicon packets.
  • Do not store Royal Icing or cookies if they already start to soften.

The photo below shows what high humidity can do to Royal Icing:

The darker the colors, the more evidence of how moisture condensation from high humidity can be seen. In the above photo, notice the areas where the dark green bled into the pink. The bleeding does not appear as much between compatible pastel colors, but it still exists, as seen below:

Ideally, you’ll protect your work, which is easier to do if it is served for eating within a day or so of completion. If, however, you need to store your cookies and your environmental atmosphere is not perfect, protect them.

If your cookies started to soften (if you can’t tell by touch, eat one), lightly re-bake them in the oven. In general, I warm my oven to 300-degrees (that is my lowest setting), turn the oven off, then insert a cookie sheet of already baked or frosted cookies. Leave them sit in the oven for 5 minutes or so.

I do not own a food dehumidifier, but I suspect if you have one, it would work, too. Most home food dehumidifiers are small, so if space matters, experiment between it and the oven method.

A recent comment exchange on Julia Usher’s Facebook Group discussed the Chefman Food Dehydrator Machine. The woman who highly recommended this machine lives in New Jersey where the wetlands and coastal areas influence the atmosphere, so I’m inclined to believe her.

Store your cookies in a dry, cool area, but not in your refrigerator. Every time you open your refrigerator’s door, atmospheric moisture condenses inside it, coating its contents with light moisture. This, in turn raises the overall humidity inside the refrigerator which lasts a long time.

If, given your environment, your icing and cookies are very dry, store them in any air-tight container, glass or plastic.

For further protection under all conditions, include silicon packets, such as available in this assortment sold on Amazon and other online retailers.

Silicon must not be eaten or mistaken for food, so obviously take care when storing treats if children are around. A product called “Food Safe” silicon packages might answer your need, but still keep all packets out of the hands of kids. If, however, you have taken precautions, but are still concerned, paste a Mr. Yuck or other poison-alert sticker on each one, like seen below:

While air-tight containers and bags exist, if you store icing and cookies that are affected by humidity, these containers simply seal the humidity inside. If humidity is a problem, even at low levels, experiment with “re-baking” a bit, then store your cooled work immediately in an air-tight container, placed in a dark, dry place.

It is easier to ship chewy cookies, than crispy. For general advice, read “5 Mistakes to Avoid When Packing & Shipping Cookies by Maggie Battista,” first published on, December 2016.



Questions? Comments? Additions? Corrections? Write to Karen Little at

Written for by Karen Little, publisher, on May 12, 2019. All rights reserved, but feel free to re-publish this article after contacting Karen so she knows where to find it.